Multi-reflecting device and backlight unit and display device having multi-reflecting architecture

ABSTRACT

A multi-reflecting device includes a plurality of double reflecting surfaces formed serially on the rear of a light guide plate having a taper shape. A light incident upon the light guide plate is double-reflected, and progress in a desired direction. The multi-reflecting structure is applied to a backlight unit and a display device so that the backlight unit and the display device can be slimmer economically.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an optical device configuredto magnify and reflect an incident light. More specifically, the presentinvention relates to a multi-reflecting device configured to magnify andemit the incident light in a desired direction with a more slimmed size,a backlight unit and a display device having a multi-reflectingstructure configured to multi-reflect an incident light.

2. Description of the Related Art

In general, display devices have been required to be smaller and flatterand to have low power consumption. Of these display devices, a liquidcrystal display controls an electric field applied to a liquid materialhaving a dielectric anisotropy to penetrate or intercept a light,thereby displaying an image or a picture. However, the liquid crystaldisplay, which is a light receiving element configured to control theamount of externally applied light and display the light on a screen,requires an additional light source to irradiate a light into a liquidcrystal panel. The display quality of the liquid crystal display dependson performance of a backlight unit as well as the liquid crystal panel.

The backlight unit includes a side-light type backlight and aperpendicular falling type backlight depending on location of the lightsource.

The perpendicular falling type backlight, which includes a plurality offluorescent lamps arranged in a line on the rear of the liquid crystalpanel, irradiates a light directly into the front surface of the liquidcrystal panel. Although the perpendicular falling type backlight issuitable for a large display device and has good brightness, it isdifficult to obtain the uniform brightness on the whole and thebacklight has large power consumption. Moreover, the liquid crystaldisplay becomes thicker.

The side-light type backlight, which includes a pipe shape line lightsource, emits a light from the line light source into the whole liquidcrystal panel with a light guide plate. The side-light type backlighthas lower power consumption and better light efficiency than those ofthe perpendicular falling type backlight.

FIG. 1 is a cross-sectional diagram illustrating a general backlightunit having a side-light type.

The general backlight unit of FIG. 1 includes a fluorescent lamp 1configured to radiate a white light, a light guide plate 2 configured tosupply the light radiated from the fluorescent lamp 1 to the frontsurface of a liquid crystal panel 8, a reflecting plate 3 configured toreflect a light streamed into the rear surface of the light guide plate2, a diffusion plate 4 configured to diffuse the light supplied from thelight guide plate 2 to improve the brightness of the light, prism sheets5 and 6 configured to concentrate the light penetrated through thediffusion plate 4 to improve an angle of a field, and a protective sheet7 configured to protect the prism sheets 5 and 6.

The light radiated from the fluorescent lamp 1 that is a light source isincident upon the light guide plate 2. The incident light is reflectedor refracted on the front and back surface of the light guide plate 2,or reflected by the reflection plate 3 and emitted into the diffusionplate 4. The angle of the reflecting plate is so small that the incidentlight from the side cannot be reflected at 90° to its progressdirection. As a result, the conventional backlight unitscattered-reflects the light using patterns formed on the surface of thereflecting plate 3. The prism sheet 5 and 6 concentrates thescattered-reflected light onto the front surface. That is, the prismsheets 5 and 6, arranged in length and width, concentrates the directionof the scattered-reflected light onto the front surface. The lightconcentrated by the prism sheets 5 and 6 is embodied into a screendepending on control of color signals of the liquid crystal panel 8.

When patterns are formed in the reflecting plate 3, the patterns resultin loss of the light, so that the brightness of about 10% is used.Furthermore, the diffusion plate 4 and the prism sheets 5, 6 areadditionally required in order to change the progress direction of thelight into the front surface of the screen. As a result, the wholemanufacturing cost of the display device is increased, implementalreliability is degraded, and the device is prevented from being thinneror lighter.

Of display devices, a projection television has been widely used whichcan embody a large screen with low cost. The projection televisiongenerates an image with an image generating unit including a small-sizedcathode ray tube (CRT) or a liquid crystal display (LCD) as an imagesource, and magnifies and projects the image into a large screen througha projection lens.

FIG. 2 is a diagram illustrating a general projection television havinga backside projection type.

The conventional projection television having a backside projection typeincludes a rectangular box-type cabinet 15 where an image generatingunit 11 configured to generate an image light like a cathode ray tube ora liquid crystal display and a projection lens unit 12 configured tomagnify and project the image light emitted from the image generatingunit 11 are built therein. A path of the image light magnified andprojected by the projection lens unit 12 is changed by a reflectingmirror 13 mounted slantingly on the rear of the cabinet 15. The imagelight whose light path has been changed is projected into a screen 14mounted on the front of the cabinet 15 so that an image is displayed.

The projection television is cheaper than a LCD TV or PDP TV, andfacilitates embodiment of a large screen to satisfy desire of consumerswho wants a large screen. However, a proper distance between the imagegenerating unit 11 for generating an image light and the screen 14 isrequired so as to secure a space where the image light proceeds formagnifying the image. As a result, the projection television has becomethicker and larger.

SUMMARY OF THE INVENTION

Technical Subject

Various embodiments of the present invention are directed at providing amore slimmed backlight unit and a display device with an improvedreflecting structure.

Technical Solution

According to one embodiment of the present invention, a multi-reflectingdevice comprises at least one or more light guide plates configured tosupply a light emitted from a light emitting unit to a front surface ofa liquid crystal panel, and at least one or more reflecting platesformed on rear surfaces of the light guide plates respectively, each ofthe reflecting plates having at least one or more reflecting surfacesconfigured to multi-reflect a light incident upon the correspondinglight guide plate from the light emitting unit and project themulti-reflected light into the front surface of the liquid crystalpanel.

According to one embodiment of the present invention, a backlight unithaving a multi-reflecting structure comprises at least one or more lightemitting units configured to emit a light, at least one or more lightguide plates, which correspond one by one to the light emitting units,configured to supply a light emitted from the corresponding lightemitting unit to a front surface of a liquid crystal panel, and at leastone or more reflecting plates formed on rear surfaces of the light guideplates respectively, each of the reflecting plates having at least oneor more multi-reflecting surfaces configured to multi-reflect a lightwhich is incident upon the corresponding light guide plate from thelight emitting unit and project the multi-reflected light into the frontsurface of the liquid crystal panel.

According to one embodiment of the present invention, a display devicehaving a multi-reflecting structure comprises an image generating unitconfigured to project an image light, a first double reflecting plateconfigured to magnify the image light from the image generating unit ina first direction and double-reflect the magnified image light to emitthe light in a second direction, and a second double reflecting plateconfigured to magnify the image light emitted from the first doublereflecting plate in the second direction and double-reflect themagnified image light to emit the light in a normal direction of ascreen.

According to one embodiment of the present invention, a display devicehaving a multi-reflecting structure comprises an image generating unitconfigured to project an image light, a first refraction/reflectionplate configured to receive the image light emitted from the imagegenerating unit, and refract and reflect the light to emit the light ina first direction, and a second refraction/reflection plate configuredto receive the image light emitted from the first refraction/reflectionplate, and refract and reflect the light to emit the light in a normaldirection of a screen.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects and advantages of the present invention will becomeapparent upon reading the following detailed description and uponreference to the drawings in which:

FIG. 1 is a cross-sectional diagram illustrating a general backlightunit having a side-light type;

FIG. 2 is a diagram illustrating a general projection television havinga backside projection type;

FIG. 3 is a cross-sectional diagram illustrating a first example of abacklight unit according to an embodiment of the present invention;

FIG. 4 is a cross-sectional diagram illustrating an example of a doublereflecting surface according to an embodiment of the present invention;

FIG. 5 is a cross-sectional diagram illustrating another example of adouble reflecting surface according to an embodiment of the presentinvention;

FIG. 6 is a cross-sectional diagram illustrating a second example of abacklight unit according to an embodiment of the present invention;

FIG. 7 is a cross-sectional diagram illustrating a third example of abacklight unit according to an embodiment of the present invention;

FIGS. 8 and 9 are diagrams illustrating a first example of a projectiontelevision having a reflecting structure according to an embodiment ofthe present invention;

FIG. 10 is a diagram illustrating a second example of a projectiontelevision according to an embodiment of the present invention;

FIG. 11 is a diagram illustrating a third example of a projectiontelevision having a reflecting structure according to an embodiment ofthe present invention;

FIGS. 12 and 13 are diagrams illustrating a fourth example of aprojection television according to an embodiment of the presentinvention;

FIGS. 14 and 15 are diagrams illustrating a fifth example of aprojection television according to an embodiment of the presentinvention;

FIG. 16 is a diagram illustrating a light refracted and reflected in arefraction/reflection plate of FIGS. 14 and 15;

FIG. 17 is a diagram illustrating a relationship between an incidentangle(χ) of an image light and a location angle (α) of arefraction/reflection plate when a medium having a refractive index of1.5 is used as the refraction/reflection plate;

FIG. 18 is a diagram illustrating a sixth example of a projectiontelevision according to an embodiment of the present invention;

FIG. 19 is a diagram illustrating a seventh example of a projectiontelevision according to an embodiment of the present invention; and

FIGS. 20 and 21 are diagrams illustrating an eighth example of aprojection television according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The present invention will be described in detail with reference to theaccompanying drawings.

FIG. 3 is a cross-sectional diagram illustrating a first example of abacklight unit according to an embodiment of the present invention. Thereference numbers of FIG. 3 are substantially similar to componentsdescribed in reference to FIG. 1.

The backlight unit of FIG. 3 includes a fluorescent lamp 1, a lightguide plate 110 (hereinafter, referred to as “LGP”), a reflecting plate120 and a protective sheet 7.

The fluorescent lamp 1 having a pipe type which is used as a radiatingunit (light source) of the backlight unit is positioned at one side ofthe LGP 110. The fluorescent lamp 1 is covered with a lamp cover (notshown).

The LGP 110 receives a light emitted from the fluorescent lamp 1 tosupply the light into the front surface of the liquid crystal panel 8.The LGP 110 has a taper shape whose thickness becomes thinner as thedistance from the light source becomes larger as shown in FIG. 3 so thata white light emitted from the fluorescent lamp 1 is evenly diffused onthe whole. Specifically, the rear of the LGP 110 is formed slant at apredetermined angle.

A reflecting plate 120 having double reflecting surfaces is formed onthe rear of the LGP 110. The double reflecting surfaces enable anincident light from the fluorescent lamp 1 to be bent at about 90° toits progress direction without being diffused in various directions sothat the progressive direction of the incident light becomes close to anormal direction of the liquid crystal panel 8. These double reflectingsurfaces are serially formed along the rear of the LGP 110 having ataper shape.

The light received from the side of the LGP 110 and magnified by the LGP110 is double-reflected by the corresponding double reflecting surfacesdepending on its incident location. That is, the double reflectingsurfaces divide the light incident upon the LGP 110 depending on itsincident location to first-reflect the light in an opposite direction tothe front surface of the liquid crystal panel 8. Then, the doublereflecting surfaces second-reflects the first-reflected light in adirection close to the normal direction of the liquid crystal panel 8.

The light incident upon the LGP 110 is not diffused in variousdirections but projected into the front surface of the liquid crystalpanel 8. The direction of the light emitted from the LGP 110 andprojected into the front surface of the liquid crystal panel 8 formsabout 90° with that of the light incident upon the LGP 110 as shown inan arrow of FIG. 2.

Each of the double reflecting surfaces is formed so that the sum of anreflection angle of the first-reflected light and an reflection angle ofthe second-reflected light may be 90° or close to 90°.

FIG. 4 is a cross-sectional diagram illustrating an example of thedouble reflecting surface according to an embodiment of the presentinvention.

Each of the double reflecting surfaces includes a first reflectingsurface 122 configured to first-reflect the light incident upon the LGP110 from the fluorescent lamp 1 in an opposite (not directly) directionof the liquid crystal panel 8 and a second reflecting surface 124configured to reflect the light reflected from the first reflectingsurface 122 toward the front surface of a liquid crystal panel 8 closeto the normal direction of the liquid crystal panel 8.

The first reflecting surface 122 has a convex oval shape to the incidentlight, and the second reflecting surface 124 has a concave oval shape tothe incident light. The order of the light incident upon the LGP 110from the fluorescent lamp 1 is reversed by the double reflectingsurface. That is, as shown in FIG. 4, the light incident upon the LGP110 in order (1), (2), (3) from the bottom is reversed into order (3),(2), (1) from the left by the first double reflecting surface, and thenprojected into the protective sheet 7 and the liquid crystal panel 8.

FIG. 5 is a cross-sectional diagram illustrating another example of adouble reflecting surface according to an embodiment of the presentinvention.

Each of the double reflecting surfaces of FIG. 5 includes a firstreflecting surface 126 different from the first reflecting surface 122of FIG. 4. That is, the first reflecting surface 126 has a concave ovalshape to the incident light. As a result, in FIG. 5, the order of thelight incident upon the LGP 110 from the fluorescent lamp 1 is the sameas that of the light reflected from the reflecting plate 120 unlike inFIG. 4.

The light incident upon the LGP 110 in order (1), (2), (3) from thebottom as shown in FIG. 5 is double-reflected in the first doublereflecting surface, and projected into the protective sheet 7 and thecrystal liquid panel 8 in order (1), (2), (3) from the left.

Although the first reflecting surfaces 122 and 126 of FIGS. 4 and 5 havea curved surface with convex and concave shape respectively, the presentinvention is not limited in these examples.

In other words, the double reflecting surface according to theembodiment of the present invention is characterized in that the path ofthe light incident upon the LGP 110 is changed so that the light may beprojected in a predetermined direction without being diffused in variousdirections. Only if the sum of a reflective angle (θ₁) of the firstreflecting surfaces 122 and 126 and a reflective angle (θ₂) of thesecond reflecting surfaces 124 and 128 is 90° or close to 90°, shapes ofthe first reflecting surfaces 122, 126 and the second reflectingsurfaces 124, 128 do not matter.

Hereinafter, the operation of the above-described backlight unitaccording to the embodiment of the present invention is explained.

The light emitted from the fluorescent lamp 1 is incident upon the LGP110. The LGP 110 has a taper shape whose thickness becomes thinner asthe distance from a light source becomes larger so that the light fromthe light source may be evenly diffused in the LGP 110 on the whole. Thelight incident upon the LGP 110 having a taper shape is reflected at apredetermined angle (θ₁) in the first reflecting surface 122 of thecorresponding double reflecting surface depending on its incidentlocation, and projected into the second reflecting surface 124. Thesecond reflecting surface 124 reflects the light reflected in the firstreflecting surface 122 at a predetermined angle (θ₂) to progress thelight in the normal direction of the liquid crystal panel 8 or its closedirection.

The double-reflected light by the first reflecting surface 122 and thesecond reflecting surface 124 is penetrated through the LGP 110 and theprotective sheet 7, and projected into the liquid crystal panel 8.

FIG. 6 is a cross-sectional diagram illustrating a second example of abacklight unit according to an embodiment of the present invention.

The backlight unit of FIG. 3 is more effective when the light incidentupon the LGP 110 is a collimated light. As a result, the backlight unitof FIG. 6 further includes a light guide 130 configured to make thelight emitted from the fluorescent lamp 1 as a collimated light betweenthe fluorescent lamp 1 and the LGP 110 to emit the collimated light intothe LGP 110.

FIG. 7 is a cross-sectional diagram illustrating a third example of abacklight unit according to an embodiment of the present invention.

The backlight unit of FIG. 7 includes a plurality of the backlight unitsof FIG. 3 so that it can be applied to a liquid crystal device having alarge screen.

As shown in FIG. 7, the edges (opposite side of the light source) of theLGPs 110 a and 110 b where a reflecting plate having double reflectingsurfaces is formed with the same structure are closely adhered to eachother so that their top surfaces are located on the same surface. Aprotective sheet 7′, which is large enough to cover the whole topsurfaces of the LGPs 110 a and 110 b, is formed over the top surface ofthe LGPs 110 a and 110 b. The number of combined LGPs can be adjustabledepending on the size of liquid crystal panel 8′.

In this way, the backlight units according to the embodiment of thepresent invention are connected with each other so that it is possibleto manufacture a large backlight unit which can be applied to alarge-scaled liquid crystal display. As a result the liquid crystaldisplay can be thinner and lighter to reduce manufacturing cost.

In the above-described embodiments, in order to broaden the reflectiveangle coating can be performed or patterns can be formed over the firstreflecting surfaces 122 126 and the second reflecting surfaces 124 and128, which may result in scattered reflection. In this case, a diffusionplate 4 is further positioned over the emitting surface of the LGP 110,that is, between the protective sheets 7 or 7′ and the LGP 110 toincrease the reflective angle of the light.

Although the above-described embodiment shows only a case the light isdouble reflected before the light incident upon the LGP 110 is emittedinto the liquid crystal panel with the double reflecting surface, thelight can be reflected triple, quadruple, etc. and emitted into theliquid crystal panels 8 and 8′.

FIGS. 8 and 9 are diagrams illustrating a first example of a projectiontelevision having a reflecting structure according to an embodiment ofthe present invention.

In this embodiment, the projection television includes two reflectingplate (hereinafter, referred to as “double reflecting plate) havingdouble reflecting surfaces uses in the above-described backlight unit toform a light path of an image light. That is, the projection televisionin this embodiment has a magnifying projection structure configured tomagnify the image light in X-axis and Y-axis directions with the twodouble reflecting plates.

The projection television in this embodiment includes an imagegenerating unit 1 c, a first LGP 210, a first reflecting plate 220, asecond LGP 230, a second reflecting plate 240 and a screen 14. The imagegenerating unit 1 c and the screen 14 are substantially similar to thecorresponding components described in reference to FIG. 2.

The first LGP 210 magnifies the image light received from the imagegenerating unit 1 c formed at one side of the first LGP 210 in theX-axis direction (horizontal direction of FIGS. 8 and 9) of the screen14, and projects the image light into one side of the second LGP 230.The LGP 210 has a taper shape whose thickness becomes thinner as thedistance from the image generating unit 1 c becomes larger. The frontsurface (hereinafter, referred to as the surface where a light isemitted from each LGP) of the first LGP 210 close to the second LGP 230is configured to be in parallel with the second LGP 230. The rearsurface (hereinafter, referred to the opposite side to the directionwhere a light is emitted from each LGP) of the first LGP 210 is formedslant at a predetermined angle.

The image generating unit 1 c, which is positioned at one side of thefirst LGP 210, projects an image light into the first LGP 210. The imagelight incident upon the first LGP 210 is magnified corresponding to thewidth of the screen 14 (the horizontal (X) axis length of the screen) bycharacteristics of the LGP 210.

The first reflecting plate 220, which is formed on the rear surface ofthe first LGP 210, double-reflects the image light incident upon theside surface of the first LGP 210 to progress the image lightperpendicular to the second LGP 230 as shown in an arrow of FIG. 8. Thefirst reflecting plate 220 includes a plurality of double reflectingsurfaces formed serially along the rear surface of the first LGP 210having a taper shape. The function and principle of the doublereflecting surface are substantially the same as those of FIG. 5. Thus,the image light is magnified in the X-axis direction by the first LGP210, and projected into the second LGP 230.

The second LGP 230 is formed with a predetermined interval apart fromthe rear side of the screen 14. The second LGP 230 magnifies the imagelight received from the first LGP 210 in the Y-axis direction (verticaldirection of FIGS. 8 and 9) of the screen 14. The function and principleof the second LGP 230 are substantially similar to those of the firstLGP 210 except the direction for magnifying the image light and its size(length and width). The image light magnified in the X-axis direction bythe first LGP 210 is re-magnified in the Y-axis direction by the secondLGP 230 as shown in an arrow of FIG. 9.

The second reflecting plate 240, which is formed on the rear surface ofthe second LGP 230, double reflects the image light incident upon theside surface of the second LGP 230. The image light received in parallelfrom the first LGP 210 as shown in the arrow of FIG. 9 is bent at about90°, and vertically projected into the front surface of the screen 14.Also, the second reflecting plate 240 is substantially similar to thefirst reflecting plate 220 except the size.

FIG. 10 is a diagram illustrating a second example of a projectiontelevision according to an embodiment of the present invention.

In this embodiment, one double reflecting plate 230, a diffusion lens250 and a collimate lens 260 are used.

In comparison with the example of FIGS. 8 and 9, the projectiontelevision of FIG. 10 is different from that of FIGS. 8 and 9 in a unitfor magnifying an image light in the X-axis direction while bothexamples include the second LGP 230 and the second reflecting plate 240for magnifying an image light in the Y-axis direction. That is, theimage light is magnified in the Y-axis direction by the second LGP 230and the second reflecting plate 240 as shown in FIG. 9 while it ismagnified in the X-axis direction by the diffusion lens 250 and thecollimate lens 260.

As a result, in this embodiment, the image generating unit 1 c, thediffusion lens 250 and the collimate lens 260 are arranged seriallytoward the bottom of the screen 14 as shown in FIG. 10.

The image light projected in parallel from the image generating unit 1 cis diffused in the X-axis direction by the diffusion lens 250, andprojected into the collimate lens 260. The image light diffused in theX-axis direction is converted into a collimated light by the collimatelens 260, and projected into one side of the second LGP 230. Then, thediffusion in the Y-axis direction is substantially the same as that ofFIGS. 8 and 9.

In the above-described embodiment, the image light is first magnified inthe X-axis direction and then in the Y-axis direction, and projectedinto the screen 14. However, the order can be changed.

FIG. 11 is a diagram illustrating a third example of a projectiontelevision having a reflecting structure according to an embodiment ofthe present invention.

In this embodiment, the projection television includes three doublereflecting plates, that is, three LGPs and three reflecting platespositioned on the rear surfaces of the three LGPs respectively.

The projection television of FIG. 11 includes an image generating unit 1c, third through fifth LGPs 310, 330, 350, and third through fifthreflecting plates 320, 340, 360.

The third LGP 310 magnifies image light received from the imagegenerating unit 1 c in the X-axis direction of the screen 14 to projectthe light into one side of the fourth LGP 330. Although the third LGP310 is substantially similar to the first LGP 210, the emissiondirection of the image light is different. That is, while the first LGP210 emits the magnified light in the Y-axis direction (upward) of thescreen 14, the third LGP 310 emits the light in a back direction (Z-axisdirection) of the screen 14.

The third reflecting plate 320, which is formed on the rear (left sideof FIG. 11) of the third LGP 310, double reflects the image lightincident upon the third LGP 310 and magnified in the X-axis direction ofthe screen 14 to be emitted in the Z-axis direction of the screen 14,that is, toward the fourth LGP 330.

The fourth LGP 330 magnifies the image light emitted from the third LGP310 in the Z-axis direction of the screen 14, and emits the magnifiedimage light into the fifth LGP 350. The fourth reflecting plate 340,which is formed on the rear of the fourth LGP 330, double reflects theimage light magnified in the Z-axis direction in the fourth LGP 330toward the Y-axis direction of the screen 14, that is, toward the fifthLGP 350.

The fifth LGP 350, which is formed with a predetermined interval apartfrom the rear side of the screen 14, magnifies the image light receivedfrom the fourth LGP 330 in the Y-axis direction of the screen 14, andprojects the image light into the screen 14.

The fifth reflecting plate 360, which is formed on the rear surface ofthe fifth LGP 350, double reflects the image light received from thefourth LGP 330 toward the screen 14.

The structure and functional principle of the third through the fifthreflecting plates 320, 340, 360 are substantially the same as those ofthe first and the second reflecting plates 220 and 240.

FIGS. 12 and 13 are diagrams illustrating a fourth example of aprojection television according to an embodiment of the presentinvention. FIG. 12 shows the side view of the projection television, andFIG. 13 shows the top view of the projection television.

In comparison with FIGS. 8 and 9, the image generating unit 1 c is movedinto the right bottom of the screen 14, and the image light emittingsurface is rotated clockwise at 90° so that the image light may beemitted in the back direction (Z-axis direction) of the screen 14. Thatis, while the image generating unit 1 c emits the image light in theX-axis direction in FIG. 8, the image generating unit 1 c emits theimage light in the Z-axis direction (backward of the screen) in FIGS. 12and 13. In the original location of the image generating unit 1 c, thereare a LGP 270 and a reflecting plate 280 for reflecting the image lightemitted from the image generating unit 1 c into the first LGP 210 (notshown by the LGPs 270 and 230 in FIG. 11). That is, the image lightemitted from the image generating unit 1 c is magnified anddouble-reflected by the LGP 270 and the reflecting plate 280, and itsprogress direction is bent at 90° to be emitted into the first LGP 210.

The structure and functional principle of the LGP 270 and the reflectingplate 280 are substantially the same as those of the above-described LGPand reflecting plate.

Thereafter, the image light magnified and double-reflected by the LGP270 and the reflecting plate 280 is magnified and double-reflectedsequentially by the first LGP 210, the first reflecting plate 220, thesecond LGP 230 and the second reflecting plate 240 as shown in FIG. 8,and then projected into the screen 4.

FIGS. 14 and 15 are diagrams illustrating a fifth example of aprojection television according to an embodiment of the presentinvention. FIG. 14 shows a magnifying projection structure in the X-axisdirection, and FIG. 15 shows a magnifying projection structure in theY-axis direction.

In this embodiment, the projection television includes an imagegenerating unit 1 c, a first refraction/reflection plate 410 and asecond refraction/reflection plate 420.

The first refraction/reflection plate 410 as a medium with apredetermined refractive index has a taper shape whose thickness ischanged with a predetermined angle. The first refraction/reflectionplate 410 has a refractive surface 412 configured to be penetrated by animage light projected from the image generating unit 1 c, and areflecting surface 414 configured to regularly reflect the image lightrefracted in the refractive surface 412.

The first refraction/reflection plate 410 refracts and reflects theimage light received in parallel from the image generating unit 1 c toprogress the image light into the second refraction/reflection plate 420while the light is bent at 90° to the incident direction. That is, theimage light emitted from the image generating unit 1 c passes throughair, and it is incident upon the first refraction/reflection plate 410through the refractive surface 412. Since the refractive index (c) ofthe first refraction/reflection plate 410 is different from therefractive index (“1”) of the air, the incident image light is refractedat a predetermined angle in the refractive surface 412 depending on therefractive index (c) of the first refraction/reflection plate 410, andprogresses toward the reflecting surface 414.

The image light refracted in the refractive surface 412 is regularlyreflected in the reflecting surface 414, and refracted in the refractivesurface 412 again to progress into the second refraction/reflectionplate 420. Due to this refraction and reflection effect, the progressdirection of the image light emitted into the secondrefraction/reflection plate 420 is bent at 90° to the progress directionof the image light incident upon the first refraction/reflection plate410. Also, the image light is magnified in the X-axis direction of thescreen 14 when the image light is refracted in the firstrefraction/reflection plate 410. As a result, the firstrefraction/reflection plate 410 has a function of magnifying an image.The refraction/reflection plate 410 includes a permeable medium such asglass, acryl and diamond.

The second refraction/reflection plate 420 has a substantially similarstructure with the first refraction/reflection plate 410. As a result,refraction and reflection of the second refraction/reflection plate 420are performed by the same principle as that of the firstrefraction/reflection plate 410.

The second refraction/reflection plate 420 refracts and reflects theimage light which is refracted and reflected in the firstrefraction/reflection plate 410 and then bent at 90°, and thenprogresses the light in the normal direction (Z-axis direction) of thescreen 14. That is, the second refraction/reflection plate 420 magnifiesthe image light magnified in the X-axis direction by the firstrefraction/reflection plate 410 in the Y-axis direction, and projectsthe image light into the screen 14. In this way, the image light emittedfrom the image generating unit 1 c is magnified sequentially in theX-axis and Y-axis directions by the first refraction/reflection plate410 and the second refraction/reflection plate 420, so that the imagelight emitted from the image generating unit 1 c is largely magnified onthe whole to be displayed through the screen 14.

FIG. 16 is a diagram illustrating a light refracted and reflected in therefraction/reflection plate of FIGS. 14 and 15.

After the image light from the image generating unit 1 c passes throughthe air and then is incident upon the refractive surface 412 of thefirst refraction/reflection plate 410, the image light is bent at apredetermined angle toward the reflecting surface 414 while penetratingthe refractive surface 412 because the refractive index (c) of the firstrefraction/reflection plate 410 is different from that of the air.Suppose that χ is an angle (incident angle) between the incident imagelight and the refractive surface 412 of the first refraction/reflectionplate 410, and θ is an angle (refractive angle) between the normal lineof the refractive surface 412 and the image light refracted in therefractive surface 412. The incident angle χ and the refractive angle θsatisfy Equation 1.

$\begin{matrix}{\frac{\sin( {\frac{\pi}{2} - \chi} )}{\sin\;\theta} = {\frac{\cos\;\chi}{\sin\;\theta} = c}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

The image light bent at θ in the refractive surface 412 is regularlyreflected at the same angle in the reflecting surface 414, andprogresses toward the refractive surface 412. The image light reflectedin the reflecting surface 414 is refracted in the refractive surface412, and emitted in a perpendicular falling direction. Suppose that y isan angle between the image light reflected in the reflecting surface 414of the first refraction reflecting plate 410 and the normal line of therefractive surface 412 and α is an angle between the image lightreceived from the image generating unit 1 c and the reflecting surface414. The angles χ and y, and the refractive index c satisfy Equation 2.

$\begin{matrix}{\frac{\sin\; y}{\sin\; x} = {\frac{\sin( {{2x} - {2\alpha} + \theta} )}{\sin\; x} = \frac{1}{c}}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

From Equations 1 and 2, a condition can be obtained so that the imagelight incident upon the refraction/reflection plate 410 is refracted andreflected in the refraction/reflection plate 410 and then emitted withits progress direction bent at 90° or close to 90°.

In other words, the relationship between χ and α can be understood sothat the refractive angle when the image light is reflected in thereflecting surface 414 and penetrates the refractive surface 412 may bethe same as the incident angle χ.

FIG. 17 is a diagram illustrating the relationship between the incidentangle χ and the α when a medium having the refractive index c of 1.5 isused as the refraction/reflection plate.

Although the first refraction/reflection plate 410 is only explained inthe above-described embodiment, the second refraction/reflection plate420 is substantially the same as the first refraction/reflection plate410.

FIG. 18 is a diagram illustrating a sixth example of a projectiontelevision according to an embodiment of the present invention.

In this embodiment, a diffusion lens 430 and a collimate lens 440 areused instead of the first refraction/reflection plate 410 in comparisonwith FIG. 12.

The diffusion lens 430 magnifies the image light from the imagegenerating unit 1 c in the X-axis direction of the screen 14. Thecollimate lens 440 converts the image light diffused in the X-axisdirection by the diffusion lens 430 into a collimated light to emit thelight into the second refraction/reflection plate 420. That is, theimage generating unit 1 c, the diffusion lens 430 and the collimate lens440 are arranged serially in the bottom of the secondrefraction/reflection plate 420. The image light from the imagegenerating unit 1 c is first magnified in the X-axis direction with lens430 and 440, and then emitted into the second refraction/reflectionplate 420.

FIG. 19 is a diagram illustrating a seventh example of a projectiontelevision according to an embodiment of the present invention.

In this embodiment, the projection television includes an imagegenerating unit 1 c, and third through fifth refraction/reflectionplates 450, 460 and 470. That is, three refraction/reflection plates450, 460 and 470 are used in the projection television of FIG. 19.

The third refraction/reflection plate 450 refracts and reflects an imagelight received from the image generating unit 1 c to magnify the imagein the X-axis direction, and bends its progress direction at 90° toprogress the light toward the fourth refraction/reflection plate 460.That is, the third refraction/reflection plate 450 emits the image lightincident toward the X-axis direction of the screen 14 in the Z-axisdirection (backward) of the screen 14.

The fourth refraction/reflection plate 460 refracts and reflects theimage light refracted and reflected by the third refraction/reflectionplate 450, and emits the light into the fifth refraction/reflectionplate 470. That is, the fourth refraction/reflection plate 460 emits theimage light incident toward the Z-axis direction of the screen 14 in theY-axis direction of the screen 14. The image light is magnified in theZ-axis direction of the screen 14 by refraction in the fourthrefraction/reflection plate 460.

The fifth refraction/reflection plate 470, which is formed apart from apredetermined distance in the rear side of the screen 14, refracts andreflects the image light received from the fourth refraction/reflectionplate 460 to emit the light in the normal direction (Z-axis direction)of the screen 14 toward the screen 14. The image light is magnified inthe Y-axis direction of the screen 14 through the refraction of thefifth refraction/reflection plate 470.

The structure and functional principle of the above-described thirdthrough fifth refraction/reflection plates 450, 460 and 470 aresubstantially the same as those of the first and the secondrefraction/reflection plates 410 and 420.

FIGS. 20 and 21 are diagrams illustrating an eighth example of aprojection television according to an embodiment of the presentinvention. FIG. 20 shows the side view of the projection television, andFIG. 21 shows the top view of the projection television.

This embodiment shows another example when three refraction/reflectionplates are used.

In comparison with the example of FIGS. 14 and 15, the image generatingunit 1 c is moved into the right bottom of the screen 14, and the imagelight emitting surface is rotated clockwise at 90° so that the imagelight may be emitted in the back direction (Z-axis direction) of thescreen 14. That is, while the image generating unit 1 c emits the imagelight in the X-axis direction in FIGS. 14 and 15, the image generatingunit 1 c emits the image light in the Z-axis direction (backward of thescreen) in FIGS. 20 and 21. In the original location of the imagegenerating unit 1 c, a sixth refraction/reflection plate 480 forrefracting and reflecting the image light emitted from the imagegenerating unit 1 c to emit the light into the firstrefraction/reflection plate 410 is positioned. That is, the image lightemitted from the image generating unit 1 c is refracted and reflected inthe sixth refraction/reflection plate 480, and its progress direction isbent at 90° to be emitted into the first refraction/reflection plate410.

In FIGS. 20 and 21, the first refraction/reflection plate 410 is notshown by other refraction/reflection plates 420 and 480.

The refraction/reflection plates used in the projection television inthe above-described embodiment may be formed of the same medium ordifferent mediums depending on design of a user.

Accordingly, a light is magnified and reflected with a multi-reflectingstructure according to an embodiment of the present invention to beemitted in a desired direction so that a backlight unit and a displaydevice can be slimmer.

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and modifications and variations are possible in light of theabove teachings or may be acquired from practice of the invention. Thus,the embodiments were chosen and described in order to explain theprinciples of the invention and its practical application to enable oneskilled in the art to utilize the invention in various embodiments andwith various modifications as are suited to the particular usecontemplated.

1. A multi-reflecting device comprising: at least one or more lightguide plates configured to supply a light emitted from a light emittingunit to a front surface of a liquid crystal panel; and at least one ormore reflecting plates formed on rear surfaces of the light guide platesrespectively, each of the reflecting plates having at least one or morereflecting surface configured to multi-reflect a light incident upon thecorresponding light guide plates from the light emitting unit andproject the multi-reflected light into the front surface of the liquidcrystal panel, wherein the multi-reflecting surface comprises: a firstreflecting surface configured to first reflect a light, which isincident upon the light guide plate from the light emitting unit, in adirection opposite to the liquid crystal panel; and a second reflectingsurface configured to second reflect the light reflected from the firstreflecting surface into the liquid crystal panel.
 2. Themulti-reflecting device according to claim 1, further comprising atleast one or more light guides positioned between the light emittingunit and the light guide plate and configured to make a light emittedfrom the light emitting unit into a collimated light to emit thecollimated light into the light guide plate.
 3. The multi-reflectingdevice according to claim 1 or 2, wherein the light guide plate isformed to have a taper shape whose thickness becomes thinner as adistance from the light emitting unit becomes larger.
 4. Themulti-reflecting device according to claim 3, wherein the firstreflecting surface and the second reflecting surface are subjected tocoating or have patterns.
 5. The multi-reflecting device according toclaim 4, further comprising a diffusion plate configured to diffuse alight from the light guide plate on an emission surface of the lightguide plate.
 6. A backlight unit having a multi-reflecting structure,the unit comprising: at least one or more light emitting unitsconfigured to emit a light; at least one or more light guide plates,corresponding one by one to the light emitting units, configured tosupply a light emitted from the corresponding light emitting unit to afront surface of a liquid crystal panel; and at least one or morereflecting plates formed on rear surfaces of the light guide platesrespectively, each of the reflecting plates having at least one or moremulti-reflecting surfaces configured to multi-reflect a light which isincident upon the corresponding light guide plate from the lightemitting unit and project the multi-reflected light into the frontsurface of the liquid crystal panel, wherein the multi-reflectingsurface comprises: a first reflecting surface configured to firstreflect a light, which is incident upon the light guide plate from thelight emitting unit, in a direction opposite to the liquid crystalpanel; and a second reflecting surface configured to second reflect thelight reflected from the first reflecting surface into the liquidcrystal panel.
 7. The backlight unit according to claim 6, furthercomprising at least one or more light guides positioned between thelight emitting unit and the light guide plate and configured to make alight emitted from the light emitting unit into a collimated light toemit the collimated light into the light guide plate.
 8. The backlightunit according to claim 6 or 7, wherein the light guide plate is formedto have a taper shape whose thickness becomes thinner as a distance fromthe light emitting unit becomes larger.
 9. The backlight unit accordingto claim 8, wherein the first reflecting surface and the secondreflecting surface are subjected to coating or have patterns.
 10. Thebacklight unit according to claim 9, further comprising a diffusionplate configured to diffuse a light from the light guide plate on anemission surface of the light guide plate.
 11. A display device having amulti-reflecting structure, the device comprising: an image generatingunit configured to project an image light; a first double reflectingplate configured to magnify the image light from the image generatingunit in a first direction and double-reflect the magnified image lightto emit the light in a second direction; and a second double reflectingplate configured to magnify the image light emitted from the firstdouble reflecting plate in the second direction and double-reflect themagnified image light to emit the light in a normal direction of ascreen.
 12. A display device having a multi-reflecting structure, thedevice comprising: an image generating unit configured to project animage light; a first double reflecting plate configured to magnify theimage light from the image generating unit in a first direction anddouble-reflect the magnified image light to emit the light in a seconddirection; and a second double reflecting plate configured to magnifythe image light emitted from the first double reflecting plate in thesecond direction and double-reflect the magnified image light to emitthe light in a third direction; and a third double reflecting plateconfigured to magnify the image light emitted from the second doublereflecting plate in the third direction and double-reflect the magnifiedimage light to emit the light in a normal direction of a screen.
 13. Adisplay device having a multi-reflecting structure, the devicecomprising: an image generating unit configured to project an imagelight; a diffusion lens configured to receive the image light from theimage generating unit and diffuse the light in a first axis direction; acollimate lens configured to convert the image light diffused in thediffusion lens into a collimated light; and a double reflecting plateconfigured to magnify the image light emitted from the collimate lens ina second direction and double-reflect the magnified image light to emitthe light in a normal direction of a screen.
 14. The display deviceaccording to one of claims 11 through 13, wherein each of the doublereflecting plates comprises: a light guide plate configured to receivethe image light and magnify the light in its progress direction; and areflecting plate formed on a rear surface of the light guide plate andhaving at least one or more double reflecting surfaces configured todouble-reflect the image light magnified in the light guide plate andchange its progress direction at 90° or close to 90°.
 15. The displaydevice according to claim 14, wherein the light guide plate is formed tohave a taper shape whose thickness becomes thinner as a distance fromthe light emitting unit becomes larger.
 16. The display device accordingto claim 14, wherein the double reflecting surface of the reflectingplate comprises: a first reflecting surface configured to first reflecta light, which is incident upon the light guide plate, in a directionopposite to a front surface of the corresponding light guide plate; anda second reflecting surface configured to second reflect the lightreflected from the first reflecting surface in a normal direction on thefront surface of the corresponding light guide plate.
 17. A displaydevice having a multi-reflecting structure, the device comprising: animage generating unit configured to project an image light; a firstrefraction/reflection plate configured to receive the image lightemitted from the image generating unit, and refract and reflect thelight to emit the light in a first direction; and a secondrefraction/reflection plate configured to receive the image lightemitted from the first refraction/reflection plate, and refract andreflect the light to emit the light in a normal direction of a screen.18. A display device having a multi-reflecting structure, the devicecomprising: an image generating unit configured to project an imagelight; a first refraction/reflection plate configured to receive theimage light emitted from the image generating unit, and refract andreflect the light to emit the light in a first direction; a secondrefraction/reflection plate configured to receive the image lightemitted from the first refraction/reflection plate, and refract andreflect the light to emit the light in a second direction; and a thirdrefraction/reflection plate configured to receive the image lightemitted from the second refraction/reflection plate, and refract andreflect the light to emit the light in a normal direction of a screen.19. A display device having a multi-reflecting structure, the devicecomprising: an image generating unit configured to project an imagelight; a diffusion lens configured to receive the image light emittedfrom the image generating unit and diffuse the light in a first axisdirection; a collimate lens configured to convert the image lightdiffused in the diffusion lens into a collimated light; and arefraction/reflection plate configured to receive the image lightemitted from the collimate lens, and refract and reflect the light toemit the light in a normal direction of a screen.
 20. The display deviceaccording to one of claims 17 through 19, wherein therefraction/reflection plate is formed to have a taper shape whosethickness is changed at a predetermined angle.
 21. The display deviceaccording to claim 20, wherein the refraction/reflection platecomprises: a refractive surface configured to refract an incident imagelight, the refracted incident image light penetration the refractivesurface; and a reflecting surface configured to reflect regularly theimage light which has penetrated the refractive surface and re-progressthe image light into the refractive surface.
 22. The display deviceaccording to claim 21, wherein the refraction/reflection plate is formedso that an angle between the refractive surface and a progress directionof an externally incident light is the same as a refractive angle ofwhich the image light reflected from the reflecting surface, isrefracted when the image light penetrates the refractive surface.